package com.yld.demo.util.redis;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

/**
 * @version 1.0
 * @description：TODO
 * @author：侯泽艺
 */
@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //解决缓存穿透
    public <R, ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis缓存查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在 isNotBlank 非空 非"" 非换行
        if (StrUtil.isNotBlank(json)) {
            //3.存在，直接返回
            System.out.println("存在");
            return JSONUtil.toBean(json, type);
        }
        //判断命中是空值
        if (json != null) {
            //返回错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回404
        if (r == null) {
            //将空值写入redis，防止缓存穿透
            stringRedisTemplate.opsForValue().set(key, "", 2L, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6。存在，写入redis
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //
    public <R, ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) throws InterruptedException {
        String key = keyPrefix + id;
        //1.从redis缓存查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在 isBlank
        if (StrUtil.isBlank(json)) {
            if ("".equals(json)) {
                return null;
            }
            //3.不存在，查询数据库
            //3.1获取互斥锁
            String lockKey = "lock" + id;
            boolean isLock = tryLock(lockKey);
            //6.2判断是否获取锁成功
            if (isLock) {
                //TODO 3.3成功，开启独立线程
                CACHE_REBUILD_EXECUTOR.submit(() -> {
                    try {
                        //查询数据库
                        R r1 = dbFallback.apply(id);
                        //写入redis
                        //5.不存在，返回404
                        if (r1 == null) {
                            //将空值写入redis，防止缓存穿透
                            stringRedisTemplate.opsForValue().set(key, "", 2L, TimeUnit.MINUTES);
                            //返回错误信息
                        } else {
                            //写入redis
                            this.setWithLogicalExpire(key, r1, time, unit);
                        }
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    } finally {
                        //释放锁
                        unLock(lockKey);
                    }
                });
            }
            Thread.sleep(200);
            return queryWithLogicalExpire(keyPrefix, id, type, dbFallback, time, unit);
        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，直接返回信息
            return r;
        }
        //5.2已过期，需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = "lock" + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if (isLock) {
            //TODO 6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4返回过期的信息
        return r;
    }

    //获取锁
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);

    }

    //释放锁
    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }

}
